1. Field of the Invention
This invention relates to a molding composition suitable for production of cores of automobile interior materials, sound absorbers of air conditioners, fiber-reinforced plastics (hereinafter xe2x80x9cFRPxe2x80x9d), constructional sound insulators, and the like.
2. Description of the Related Art
Cores of automobile interior materials, sound absorbers of air conditioners, FRP, constructional sound insulators, and the like are produced from molding compounds mainly comprising fiber, a phenolic resin, and an amine curing agent to secure sufficient strength (see, for example, JP-A-57-55962 and JP-A-7-1666). However, phenolic resins react thermally to produce formaldehyde, and the amine curing agent has the problem of smell.
Powdered molding compounds comprising a diallyl phthalate prepolymer and/or a crystalline unsaturated polyester resin, fiber, and a curing agent are known (see JP-A-5-169475). However, the diallyl phthalate prepolymer has a low iodine value and fails to achieve a high crosslinking density so that the resulting molded article has insufficient strength.
A molding composition comprising a non-crystalline unsaturated polyester and an ethylenically unsaturated group-containing monomer having compatibility with the unsaturated polyester and a molding composition further comprising a polymerization initiator are also known (see JP-B-2-31090). Acting as a crosslinking agent, the ethylenically unsaturated group-containing monomer compatible with an unsaturated polyester brings about improved strength but has the problems of smell and safety.
An object of the present invention is to provide a molded article having sufficient strength and heat resistance for practical use and improved safety and smell.
Another object of the present invention is to provide a molding composition suitable for producing such a molded article.
The present invention relates to a molding composition comprising (A) a fibrous material, at least one of (B) a nonlinear unsaturated polyester and (C) a nonlinear unsaturated polyester-polyamide, and (D) a radical generator. The invention also relates to a molded article obtained by molding the molding composition.
According to the present invention, use of components (B) and/or (C) provides a molded article with sufficient strength for practical use and free from the problems of formaldehyde generation and smell.
The fibrous material as component (A) is not particularly limited and includes inorganic fibers such as glass fiber and organic fibers such as synthetic resin fibers and natural fibers. Organic fibers of cotton, flax, wool, silk, nylon, etc. are preferred from the standpoint of flexibility and heat insulation of a molded article. Component (A) can be used in the form of yarn or fabric, either woven or nonwoven.
The nonlinear unsaturated polyester as component (B) is not particularly limited as long as it is nonlinear. From the viewpoint of molding properties in high temperature and strength of molded articles, crystalline polyesters are preferred. The raw monomers providing component (B) are not particularly limited and include di- or higher polyhydric alcohol components, di- or higher polycarboxylic acid components, such as carboxylic acids or anhydrides or esters thereof, and addition polymerizable unsaturated group-containing monomers.
Preferred dihydric alcohol components include a bisphenol A-alkylene oxide adduct (containing 2 or 3 carbon atoms in the alkylene moiety; average mole number of alkylene oxide added: 1 to 10), ethylene glycol, propylene glycol, 1,6-hexanediol, 1,4-butanediol, bisphenol A, and hydrogenated bisphenol A.
Preferred tri- or higher polyhydric alcohol components include sorbitol, 1,4-sorbitan, pentaerythritol, glycerol, and trimethylolpropane.
The dicarboxylic acid components include various dicarboxylic acids and succinic acid which is substituted with an alkyl or alkenyl group having 1 to 20 carbon atoms, anhydrides of these acids, and alkyl esters of these acids having 1 to 12 carbon atoms in the alkyl moiety thereof. Maleic anhydride, fumaric acid, terephthalic acid, and C2-20 alkenyl-substituted succinic anhydride are preferred.
Preferred tri- or higher polycarboxylic acids include 1,2,4-benzenetricarboxylic acid (trimellitic acid), an anhydride thereof, and an alkyl ester thereof having 1 to 12 carbon atoms in the alkyl moiety.
The addition polymerizable unsaturated group-containing monomers include fumaric acid, maleic acid, maleic anhydride, and itaconic acid, with fumaric acid and maleic anhydride being preferred.
The nonlinear unsaturated polyester as component (B) can be prepared by allowing a mixture comprising the above-described monomers to react at 150 to 250xc2x0 C. for 5 to 20 hours in a nitrogen atmosphere. It is acceptable to use a monohydric alcohol component or a monocarboxylic acid component for molecular weight regulation and a commonly employed catalyst for esterification, such as dibutyltin oxide, for reaction acceleration.
The nonlinear unsaturated polyester-polyamide as component (C) is not particularly restricted as long as it is nonlinear. From the standpoint of molding properties in high temperature and strength of molded articles, crystalline polymers are preferred. Component (C) can be obtained from a monomer mixture comprising an amine monomer in addition to the monomers used to prepare component (B). Examples of the amine monomers include various known polyamines, aminocarboxylic acids, amino alcohols, and lactams. Preferred amine monomers are ethylenediamine, hexamethylenediamine, xylylenediamine, and xcex5-caprolactam.
The amine monomer is preferably present in component (C) in a proportion of 1.0 to 20.0 mol %.
It is preferred for components (B) and (C) to contain 0.1 to 30% by weight, particularly 0.1 to 20% by weight, of a tri- or higher polyhydric alcohol and/or a tri- or higher polycarboxylic acid derivative based on the total constituent monomers. Such a molding composition exhibits satisfactory molding properties to provide a uniform molded article with further improved strength in ambient temperature and high temperature.
From the viewpoint of molded article strength, it is also preferred for components (B) and (C) to contain 20% by weight or more, particularly 30% by weight or more, of at least one addition polymerizable unsaturated group-containing monomer based on the total constituent monomers.
One or more kinds of component (B) and/or one or more kinds of component (C) can be used in combination.
It is preferred for components (B) and (C) to have an iodine value of 40 or greater, particularly 45 or greater, especially 60 or greater, to secure strength of molded articles.
Of the polymers as component (B) or (C) those having crystallinity preferably have a melting point of 90xc2x0 to 160xc2x0 C. as a main peak top temperature of the DSC curve measured at a heating rate of 10xc2x0 C./min in an onset method and a melt viscosity of 100 Paxc2x7s or less at a temperature higher than that melting point by 20xc2x0 C.
The radical generator as component (D) include peroxides, persulfates, and azo compounds, with peroxides and persulfates being preferred. Lauroyl peroxide, dibutyl peroxide, dicumyl peroxide, and sodium persulfate are particularly preferred. It is preferred for the radical generator to have a half-life of 7 days or longer at 40xc2x0 C. to secure the preservability, stability and the like of the molding composition. Taking the molding time into consideration, a still preferred half-life is within 10 minutes at 250xc2x0 C.
If desired, the molding composition of the invention can contain known additives, such as a curing aid (e.g., diallyl phthalate or triallyl phthalate), a lubricant (e.g., amide wax, synthetic wax, latices, or fatty acid metal salts), a filler (e.g., talc, calcium carbonate or aluminum hydroxide), and so forth.
The molding composition of the invention is prepared by compounding the above-described components in a Henschel mixer, a fluidized bed mixer, and the like.
The compounding ratios of the components are not particularly limited as long as the molded articles obtained therefrom have sufficient strength for practical use. A preferred content of component (A) is 29 to 99% by weight, particularly 50 to 98.9% by weight, based on the total composition from the standpoint of the specific gravity and strength of molded articles. A preferred total content of component (B) and component (C) is 0.5 to 70% by weight, particularly 0.9 to 50% by weight, based on the total composition from the viewpoint of the strength and specific gravity of molded articles. A preferred content of component (D) is 0.1 to 30% by weight, particularly 0.1 to 20% by weight, based on the total composition from the standpoint of the strength and specific gravity of the molded articles. The amounts of the additives optionally incorporated, such as a catalyst, a curing aid, a lubricant, and a filler, can be selected appropriately to obtain the desired effects.
Known molding methods can be adopted with no particularly restriction for obtaining molded articles of the present invention from the above-mentioned molding composition, such as compression molding, laminated molding, injection molding, and extrusion. Prior to molding, the composition may be subjected to remaining heat or heating.
The molded article according to the invention preferably has a bend strength of 100 kg/cm2 or more, particularly 120 kg/cm2 or more, as measured in accordance with JIS K6911. That is, the molded article exhibits sufficient strength for practical use and also satisfactory heat resistance and therefore suited for use as cores of automobile interior materials, sound absorbers of air conditioners, FRP, constructional sound insulators, and the like.